Although it is often proposed that chromosomal proteins act as gene regulators in eukaryotes, the precise ways in which specific chromosomal proteins affect the structure and function of particular genes are not at all clear. The object of study is the chromatin which codes for the ribosomal RNA genes (rDNA chromatin). We have been using the slime mold, Physarum polycephalum, for these studies because we have devised methods to purify rDNA chromatin. Some experiments involving the developmental regulation of rRNA genes will utilize either oocytes from the African clawed toad, Xenopus laevis, or embryos from the fruit fly, Drosophila melanogaster. We have four goals in this project. First, we intend to complete our analysis of the protein composition of rDNA chromatin, both on the transcriptionally active gene and adjacent, inactive chromatin. We also intend to compare proteins associated with the gene before and after transcription commences in a developmentally regulated system. Second, we plan to continue our studies of the regulation of higher order structure of rDNA chromatin. We plan to follow both morphological and biochemical properties of rDNA injected into oocytes at developmental stages before and during normal rRNA transcription. Third, we plan to establish the precise mechanism of inheritance of chromosomal proteins during DNA replication by using density labelling methodology already perfected in our laboratory. Finally, we wish to study the dynamics of nucleosome turnover in the gene and adjacent non-transcribed chromatin in Physarum, again by density labelling. This experiment will test the hypothesis that histones in the gene region are less stably associated with DNA than those from regions that are not transcribed.